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Old 02-06-2016, 10:44 PM   #11 (permalink)
Studying Brick economics
 
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Originally Posted by ChopStix View Post
The 2 things that helped me the most (thus far) have been narrow light weight tires with steel wheels. And having my stock computer programmed with the low altitude factory program.

Most aluminum wheels are actually heavier than stock steel wheels in the same size. And there was a recall on the stock computer for my van. The new program they put in made a giant difference.

My best thus far has been 26mpg highway. With my goal being 30mpg. My next mods will be new tires for summer, domed hub caps, electric fan conversion, and power pulleys. I wanna see where these leave me before messing with any aero mods. But a partial grill block, front and side skirts are in my future.
I have actually already bought a set of OEM 20" wheels for a 2015 GMC Sierra. They are much better looking than the factory wheels and I don't expect to lose more than 1mpg while running them in the summer. We will see though.

Also I'm considering a 2wd swap not for mpg reasons but because the front diffs in these aren't built well and have to be rebuilt quite often to stay quiet running. Going from AWD to 2wd would be a massive jump in highway mileage as well I'm sure.

I will be getting the ECU reprogrammed shortly for better eco shift points and leaner running in the low to mid load areas of my map.

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Old 02-07-2016, 11:43 AM   #12 (permalink)
Studying Brick economics
 
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Join Date: Feb 2016
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Tahoe - '04 Chevrolet Tahoe LT
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05-06 OEM Airdam, also you can't see it but I have a 75% grill block on as well


My new wheels, can't wait to get these on!


Roofrack delete, looks way better!


Electric fan conversion from 05 model


Overall distance side profile
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Old 02-07-2016, 01:05 PM   #13 (permalink)
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While your converting it to 2wd you could swap in a manual transmission that would make a massive difference in fuel economy and reliability
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Old 02-07-2016, 02:52 PM   #14 (permalink)
Studying Brick economics
 
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Quote:
Originally Posted by mazdamx640 View Post
While your converting it to 2wd you could swap in a manual transmission that would make a massive difference in fuel economy and reliability
I have already been eyeballing T56 and nv4500 swaps.
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Old 02-08-2016, 10:22 AM   #15 (permalink)
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That is the problem with 4wd.
Its guaranteed 4wd when things will bind and break and its guaranteed 2wd when you actually need it.
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Old 09-03-2016, 11:24 PM   #16 (permalink)
Studying Brick economics
 
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Well it's been a rough summer for gas mileage.

The wheels and lowering happened about the same time so I think one negated the other to be honest. I still need to get the ecu retuned again, just haven't had the down time to send it in for a reflash.

I work all day in the NC heat so driving back and forth to work with the AC off just isn't an option for me personally. The heat has also been severe enough that I removed the grill block and am now 100% full airflow. All of these things have led me to poor mileage.

I am starting to keep track again of fuel mileage as I was getting very discouraged when seeing 15.xx mpg overal per tank so I stopped keeping track.

The 75% upper grill block may turn into 100% once the average daily temp goes below 70. I'll just rely on the lower grill to do the trick. Should be fine. I am also going to be actually accomplishing the belly pan on the bottom too.

She looks much better than the day I got her.

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Old 09-05-2016, 02:26 AM   #17 (permalink)
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Are you sure that your 2004 GM vehicle doesn't do DFCO? The way to tell is if you have a mpg gauge, it will say 99.9 mpg when you coast. Otherwise, I don't know how you would know.
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Old 09-06-2016, 03:27 PM   #18 (permalink)
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Quote:
Originally Posted by Andrewhans View Post
Well it's been a rough summer for gas mileage.

The wheels and lowering happened about the same time so I think one negated the other to be honest. I still need to get the ecu retuned again, just haven't had the down time to send it in for a reflash.

I work all day in the NC heat so driving back and forth to work with the AC off just isn't an option for me personally. The heat has also been severe enough that I removed the grill block and am now 100% full airflow. All of these things have led me to poor mileage.

I am starting to keep track again of fuel mileage as I was getting very discouraged when seeing 15.xx mpg overal per tank so I stopped keeping track.

The 75% upper grill block may turn into 100% once the average daily temp goes below 70. I'll just rely on the lower grill to do the trick. Should be fine. I am also going to be actually accomplishing the belly pan on the bottom too.

She looks much better than the day I got her.

I missed this thread the first time through...

You are doing all the things I would suggest... but you have exactly the worst version of the Tahoe to start with for mpg. What gear ratio do you have? I'm guessing that is hurting you as well.

When shopping for a Tahoe for my wife, I picked out this one specifically for mileage:


It was lowered a little (didn't actually realize that when we bought it), and had 22" wheels, but was otherwise stock. 2wd, 4.8L V8, 3.23 gears. Now has 20" wheels from an '08 LTZ Silverado with 45psi in the tires. It's an '05 so it already has the OEM air dam (which is plenty, I wouldn't go lower) and the e-fan. We regularly see 20-25mpg hwy. Average is quite a bit lower though, since she does mostly city driving and has a rather heavy foot.

You can check out my Silverado thread below for some ideas if you like. Pictures were reposted late in the thread: http://ecomodder.com/forum/showthrea...tml#post441133
A couple pointers for blocking the grill:
1) Do you have a tranny cooler on the drivers side, in front of the radiator? I think this is standard on all of these trucks. I would strongly recommend leaving a hole for airflow there, especially if you tow.
2) The slots in the bumper should also bring air into the radiator.
3) Blocking from the front was much more effective for me than blocking the rear.

Good luck to you, I'm curious to see how you do.
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Old 09-06-2016, 05:12 PM   #19 (permalink)
Studying Brick economics
 
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Yes, I agree completely that I have the worst version for mpg. AWD 5.3 and 3.73 gears. None of which are helping me out.

I wanted the 5.3 as they make more power and the difference in mpg is not that large at all. The part that really kills it, is the AWD.

I also am keeping 40 to 45 in the tires as well. We have the same size wheels and most likely the same tires as well. 275/55/20

Transmission cooler is in the center, right behind the Chevy emblem. On the drivers side is the powersteering cooler. I have both. I use the Torque App to both monitor all of my temps and to tune my driving. That's why I removed my 75% grill block as the trans temps were becoming to high for my liking on a day to day no load highway driving(175-185)

The slots in the bumper have a black plastic fillers. There is no airflow through them for mine. The only airflow I would be getting would be through the lower opening. I don't think I will be blocking from the front due to appearances(I really like how it looks lol)


It turns out my ECU does to DFCO. I just haven't been watching at the right times yet. I noticed it the other day. I would like to get the tuner to have it enter DFCO sooner and hold it longer.
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Old 09-06-2016, 06:19 PM   #20 (permalink)
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Quote:
Originally Posted by Andrewhans View Post
Yes, I agree completely that I have the worst version for mpg. AWD 5.3 and 3.73 gears. None of which are helping me out.

I wanted the 5.3 as they make more power and the difference in mpg is not that large at all. The part that really kills it, is the AWD.

I also am keeping 40 to 45 in the tires as well. We have the same size wheels and most likely the same tires as well. 275/55/20

Transmission cooler is in the center, right behind the Chevy emblem. On the drivers side is the powersteering cooler. I have both. I use the Torque App to both monitor all of my temps and to tune my driving. That's why I removed my 75% grill block as the trans temps were becoming to high for my liking on a day to day no load highway driving(175-185)

The slots in the bumper have a black plastic fillers. There is no airflow through them for mine. The only airflow I would be getting would be through the lower opening. I don't think I will be blocking from the front due to appearances(I really like how it looks lol)


It turns out my ECU does to DFCO. I just haven't been watching at the right times yet. I noticed it the other day. I would like to get the tuner to have it enter DFCO sooner and hold it longer.
At 285hp for the 4.8L vs 295hp for the 5.3L, I was fine with the smaller engine. They are pretty close in performance, with a slight edge in power for the 5.3 and economy for the 4.8. In spite of the high gears, it tows our 4500+ lb travel trailer just fine.

I'm probably mistaken on the cooler then. Neither my old Silverado nor the Tahoe have the other cooler you are referring to behind the emblem and neither have tranny temp sensors. As long as you are monitoring the temps, you should be fine.

From memory, both my Silverado and Tahoe have the slots completely open, with flaps behind it that deflect air towards the radiator. I'll double check on the Tahoe tonight.

I understand not wanting to alter the looks. My wife tolerates it on my Civic but will raise hell if I touch her Tahoe.

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